The present invention relates to a method for preparing an agent for removal of dissolved phosphorus compounds from water and an agent for removal of dissolved phosphorus compounds from water. This agent allows for binding and subsequent removal of phosphorus from water.
The world population growth and the changes in the energy management cause that the global demand for both food and biofuels is rising. The efficiency of agricultural production is closely related to the use of phosphate fertilizers for manufacturing of which currently utilized is 90% of all phosphorus obtained from mining phosphate rocks. As a result, larger and larger amounts of this element enter the phosphorus cycle in the environment. Both a sedimentic character of this cycle and a low mobility of phosphorus in the abiotic nature leads to its practically irreversible dissipation in the terrestrial and aquatic ecosystems. An increased fertility of these ecosystems, commonly called eutrophication, disturbs an equilibrium of the aquatic environments and limits the biodiversity of terrestrial environment. A loss of ecological balance is not the only side effect of an excessive dissipation of phosphorous. The natural phosphates similarly to petroleum are the irreversible resources. Although petroleum can be substituted by carbon or natural gas, there is no such substitute for phosphorus. Exhaustion of mineral resources of phosphates which are the main and cost-effective source of phosphorus on the Earth, would lead to deficiency of phosphorus fertilizers, and thereby to a threat to food production throughout the world. It has been estimated that currently recognized reserves will be exhausted over the next 130 years; the potential reserves may be estimated for more than 360 years.
Phosphorus does not disappear (as hydrocarbons) after “consumption”, it can be practically subjected to infinite recycling, and this should be taken into account in agriculture and food distribution systems. Many studies have been carried out on the alternative sources of phosphorus in the human food chain, among them as the most important recognized are: municipal and industrial wastewaters, sewage sludge, farrows and waste from meat industry. The majority of developed technologies concern the recovery of phosphorus from wastewaters, among them the most numerous group constitute the crystallization methods of struvite ammonium-magnesium phosphate which properly granulated may be used as fertilizer. As follows from these studies, the problem of phosphorus recovery has a technical and economical character; currently working installations are not cost-effective.
There has been no solution for selective removal of excessive amounts of phosphorus from the aquatic ecosystems. The only method of phosphorus removal outside the aquatic ecosystem is dredging of bottoms sludge, which is a very expensive method, requires building of special silting fields, and additionally may cause irreversible negative alteration in the entire ecosystem. There are several methods aimed at binding of dissolved phosphorus compounds into the sparingly soluble forms. The essential drawback of these methods is the introduction of large quantity of chemical compounds no native for the aquatic ecosystems which remain in there together with phosphorus and constitute a potential source of secondary pollutants.
From publication MIN H. J., HERING J. G., Water Environ. Res. 71: 169-175 (1999), known is a modification of calcium alginate with the use of Fe(III), where the adsorbents were prepared for the removal from water the oxygen anions containing Se(IV), Cr(VI) and As(V). In the available literature the only system of this type for the adsorption of phosphate ions from the aqueous phase was an alginate/zirconium sulphate matrix which was characterized by better sorption properties than zirconium sulphate in the powdered form. [Yeon et al., Korean J. Chem. Eng., 25(5): 1040, (2008)]. A very high price of zirconium salt and a complex technology for the preparation of systems thereof, requiring the application of surfactants, significantly restricts the possibility of practical utilization of said solution. The research carried out in the case of other biosorbents confirmed that the immobilization of iron in their structure significantly enhances the affinity of phosphate ions for these biopolymers [Eberhardt et al., Bioresour. Technol. 97, 2371 (2006) and Eberhardt and Min, Bioresour. Technol. 99: 626 (2008)].